A Comparative Study of Code Clone Genealogies in Test Code and Production Code

Recent research has shown that clones occur far more often in test code than in production code. This is explained by the typical template of unit test code (the setup-stimulate-verify-teardown cycle), a template which lends itself well to parameterisation of proven solutions. However, little is known on how these clones evolve over time. In this paper, we compare the evolution of clones in test code with those in production code. Based on a quantitative and qualitative study of eight representative open-source systems, we conclude that clones in test code are inherently different than clones in production code throughout development. As a consequence, consistent maintenance and tracking of test clones becomes more important, hence the need for special purpose clone tracking and management tools.